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Design Volume Calculations -Lower Sump Area Drainage Area (acres) 1.13 Design Event 100 yr. Storm Design Precipitation 3.2 Average CN 89 Calculated S 1.23595505618 Description Exposed gravel and rocky soil Calculated Runoff Volume (Q) 2.08 Calculated Runoff Volume (acre-ft.) 0.20 Ponding Percentage 5.00 Actual Runoff Volume (acre/ft.) 0.19 As shown on the Hydrology Map, this sump will have the design capacity of .22 acre feet allowing for extra volume for sediment storage. Collection ditches will be installed that direct water from the disturbed areas into the sump. These ditches will be v-ditches of at least 1.0 feet deep and 2.OH:1.OV sideslopes. No lining will be employed since the grades are mild and they aze leading to sediment sumps. Alternative Sediment Control (SAE) Topsoil Stockpile # 2 Once topsoil is removed from this stockpile and while the area is final-graded, a berm of 24" height will be placed around the former pile azea (2.69 acres) to prevent erosion from the area. This berm will be placed with a small dozer and will have 2H:1 V sideslopes. Once final bond release is granted, this berm will be regraded into the surrounding terrain. Stream Channel Reconstruction (Carbon Junction Canyon) Carbon Junction Canyon will be reconstructed and permanently diverted as detailed below. The work involves a diversion of 1962 feet that will be riprap lined and will have one culvert crossing under the main access road. The channel itself will be 14' wide after lining and varies in depth from l.9 feet to 2.8 feet for segment 6, including freeboard. Technical Revision to Appendices 5-9 and 5-10 of this coal permit shows that the peak flow for the upper segment (above the junction with the mine access road) is 346 cfs for the 100 year event for a drainage area of 188 acres. This was verified to be con•ect. This flow was used to design the diversion channel. TR09, TRl l 5-8 Revised 3/98, 8/02